The invention relates to a wet rotor-type pump, i. e. a pump and motor unit e. g. comprising a centrifugal pump and an electric-direct-current motor. Such wet rotor-type pumps are in particular suitable for pumping cooling medium in vehicle motors.
From DE 195 45 561 a wet rotor-type pump having a pump impeller is known, which pump impeller takes in a liquid or gaseous fluid through an intake duct and feeds it towards a discharge duct. The pump impeller is mounted on a shaft. Said shaft also carries a rotor of a motor. For cooling the motor and any electronical components, the fluid flowing around the motor rotor is used. For feeding electrically conducting liquids, the motor rotor is surrounded by a slotted pot. The stator package of the motor with the windings is arranged outside the slotted pot which is preferably made of plastic material. The slotted pot, which is provided with a slot extending between the motor rotor and the inside of the pot and through which a fluid can flow, ensures sealing of the motor rotor towards the surroundings. Wet rotor-type pumps used for pumping liquids which are not electrically conducting, e. g. gasoline, do not comprise a slotted pot since sealing towards the stator package and the windings is not necessary.
Motor rotors, which generally comprise a plurality of solenoids and a rotor body, i. e. a carrier body for the solenoids, must be fluid-cooled and thus protected against corrosion. This is in particular required when water or coolants are pumped since these are strongly corrosive media. It common practice to surround the motor rotor, which is pressed on the common shaft, with a shell of high-grade steel acting as a protective means. For this purpose, a cylindrical shell of high-grade steel is pushed over the motor rotor and closed with two caps of high-grade steel. The high-grade steel shell and the caps as well as the caps and the shaft are welded to each other. This forms a seal for the motor rotor. This type of sealing is a very complex process, in particular in the case of large-scale production.